Keypads are common input/output devices used in computer systems, cell phones, appliances, automated teller machines (ATMs), and the like. A keypad electrically senses the depression of one or more keys by the user and provides corresponding signals to other circuitry, such as a microprocessor or microcontroller, for processing.
Some keypad applications require enhanced security features. For example, an ATM keypad is susceptible to hacking whereby a hacker can solder wires surreptitiously to the key sensors to detect personal identification codes as they are entered by an unsuspecting user.
There are several known anti-theft measures for keypads, including electrical sensors that detect attempts to desolder integrated circuits, which sensing can be used to shut down the system. Other sensors can detect attempts to separate layers of the keypads to tap into the key sensors. While these techniques make it more difficult for hackers to tap into the key sensors, new and better techniques would be desirable.
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